Conditional compiling for android

[sapna....@gmail.com]

As per the documentation in https://golang.org/pkg/go/build/ :

Using GOOS=android matches build tags and files as for GOOS=linux in addition to android tags and files.

So what if I want to compile a file on android but not for linux, because I have multiple targets , one of them being linux and the other one being android.

Any suggestions on this will be greatly appreciated, thanks !

[andrey mirtchovski]

you can do this for the pure linux stuff:

// +build !android,linux

[Sapna Todwal]

I already tried this and it doesn't work . Also I need a way to enable certain code only for pure android and not linux. Any suggestions ??

[Nigel Tao]

On Wed, Aug 31, 2016 at 4:45 AM, Sapna Todwal <sapna....@gmail.com> wrote:
> I already tried this and it doesn't work .

That's odd. It should work. What are your filenames? What do your "//
+build" lines look like exactly?

> Also I need a way to enable
> certain code only for pure android and not linux. Any suggestions ??

// +build android

[aashish...@gmail.com]

I have similar situation where I need to compile a package specifically for android and other specifically for linux.

I have included constraints mentioned above for pure linux and pure android compilation but still both files

are getting built and I get error.

GOOS=android

GOARCH=arm

Android specific files are named as *_android.go with build constraint "// +build android"

and 

Linux specific files are named as *_linux.go with build constraints "// +build !android,linux"

Thanks in advance.

[Hyang-Ah Hana Kim]

Strange. Can you share an example for repro?

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[Dave Cheney]

The build system considers android and Linux to be the same for historical reasons.

[Hyang-Ah Hana Kim]

Partly true.

Build tags like !android should prevent inclusion of the file.

Files named with _android suffix or with android buildtag should be included only for android.

https://go.googlesource.com/go/+/master/src/time/zoneinfo_android.go

https://go.googlesource.com/go/+/master/src/time/zoneinfo_unix.go#5

On Thu, Feb 1, 2018 at 2:40 PM, Dave Cheney <da...@cheney.net> wrote:

The build system considers android and Linux to be the same for historical reasons.

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[aashish...@gmail.com]

Thanks for getting back.

I finally got it to work after some experimentation on test project. 

Solution

Added tag android for android only file and named it with suffix _android

// +build android

And for linux only file added

// +build !android

Below env are set as mentioned earlier

GOOS=android

GOARCH=arm

And build command used is 

go build --tags android <main_package>

Build constraint line is added at the top of the file followed by a blank line.

They don't work if I add them after copyright header (block comment) with preceding and following blank line. 

May be only line comments are allowed above the build constraint line as mentioned on official page and not block comments.

Constraints may appear in any kind of source file (not just Go), but they must appear near the top of the file, preceded only by blank lines and other line comments. These rules mean that in Go files a build constraint must appear before the package clause.

On Friday, February 2, 2018 at 2:26:28 AM UTC+5:30, Hyang-Ah Hana Kim wrote:

Partly true.

Build tags like !android should prevent inclusion of the file.

Files named with _android suffix or with android buildtag should be included only for android.

https://go.googlesource.com/go/+/master/src/time/zoneinfo_android.go

https://go.googlesource.com/go/+/master/src/time/zoneinfo_unix.go#5

On Thu, Feb 1, 2018 at 2:40 PM, Dave Cheney <da...@cheney.net> wrote:

The build system considers android and Linux to be the same for historical reasons.

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